Stories from DEP is a collection of feature articles
published in DEP's internal newsletter, Weekly Pipeline.
This article was originally published July 12, 2011.

Lost in Yonkers? Head South from Hillview

Situated in Yonkers, the Hillview Reservoir is an imposing presence for drivers on the New York State Thruway. As they whiz by the 90-acre man-made lake, few drivers are aware that what they are passing is one of the most critical pieces of infrastructure in the city’s water distribution system. Built from 1909 to 1915 by a DEP predecessor agency, the Board of Water Supply, the Hillview Reservoir is essentially a huge holding tank and pressure balancing mechanism that regulates the flow of water from the upstate aqueducts and reservoirs into City Water Tunnel Nos. 1, 2, and 3.

The Hillview Reservoir marks the point at which upstate water first enters the city’s complex distribution system. In order to manage this transition, a large reservoir is necessary to serve both as a holding tank to balance pressure and ensure that the water maintains enough pressure when it leaves the reservoir and travels all the way to Staten Island, a distance of some 30 miles. As the city wakes up each morning and demand for water increases, Hillview acts as a reserve tank to supply the three city water tunnels with the water they need to meet the day’s demand. And as demand decreases during the night, water from the upstate aqueducts refills the depleted reservoir to ensure that it is fully stocked for the next morning. As a result, reservoir levels are constantly fluctuating.

In addition to its role as a flow regulator and holding tank, the Hillview Reservoir is the point at which secondary disinfection of the water supply occurs. DEP treats its water supply with various chemicals that provide a range of benefits both to customers and to the distribution infrastructure itself. Each day, the DEP employees at Hillview add chemicals to the water supply to disinfect the water, balance pH levels, and control corrosion within the distribution system. This daily chemical treatment is critical to the safety of New York’s drinking water.

Although Hillview is located in Yonkers, it represents the beginning of the in-city distribution system and is operated and maintained by more than 50 employees from the Bureau of Water and Sewer Operations (BWSO). Given its critical mission, Hillview is staffed 24 hours a day, seven days a week by around-the-clock shifts. These DEP employees perform a variety of duties including pump adjustments, gatehouse inspections, and water flow tracking. They also implement the secondary disinfection program by monitoring pH levels, taking water samples, and ensuring that chemical targets are being met. One of their most important jobs is to maintain regular communication with employees from the Bureau of Water Supply (BWS) at Kensico Reservoir to ensure that the flow of water is being properly managed.

Although most people drive right by without even noticing it, the Hillview Reservoir provides a vital service that should not be taken for granted. For security reasons the reservoir is not available to the public and DEP Police take a number of preventative steps to keep the reservoir safe. Vijay Rao, the operations manager for all in-city reservoirs, notes that “after the FDNY and the NYPD, we are the unsung heroes of New York City.”

So the next time you’re driving south on the New York State Thruway, take a moment to appreciate the bright blue waters of Hillview Reservoir, and the hard work of the DEP employees who operate our complex water supply system.